1. Field of the Invention
The present invention relates to personal computer systems and more particularly to a split system personal computer which includes a media console containing user interactive components (e.g., floppy disk drive, power switch) coupled to a processing unit having system components (e.g., central processing unit, memory, hard disk drive) via a cable and wherein a system management interrupt (SMI) is used to control devices which exist in both the media console and the processing unit.
2. Description of Related Art
Personal computer systems are well known in the art. Personal computer systems in general, and IBM Personal Computers in particular, have attained widespread use for providing computer power to many segments of today's modern society. Personal computers can typically be defined as a desktop, floor standing, or portable microcomputer that is comprised of a system unit having a single central processing unit (CPU) and associated volatile and non-volatile memory, including all RAM and BIOS ROM, a system monitor, a keyboard, one or more flexible diskette drives, a fixed disk storage drive (also known as a "hard drive"), a so-called "mouse" pointing device, and an optional printer. One of the distinguishing characteristics of these systems is the use of a motherboard or system planar to electrically connect these components together. These systems are designed primarily to give independent computing power to a single user and are inexpensively priced for purchase by individuals or small businesses. Examples of such personal computer systems are IBM's Personal Computer AT and IBM's Aptiva.
Historically, a personal computer (PC) was a relatively large box that sat on top of a desk and contained all of the electronics--the processor, memory, IO devices, floppy disk drive, etc. This was known as the system unit and required a significant amount of desktop work space. The monitor was traditionally a cathode ray tube (CRT) that was placed on top of the system unit. The keyboard and (eventually a mouse) was placed in front of the system unit to provide for user input. Accordingly, these "desktop" computer systems combined all PC functions and accessibility in one enclosure on the desktop where significant space is required and noise sources are relatively close to the user. In addition, there was no way to compact the elements when the PC was not in use.
In order to reduce the clutter that a personal computer caused on the desktop, a tower design soon emerged that moved the system unit components into a tower form-factor that sat along-side the desk. The CRT now sat directly on the desk with the keyboard and mouse in front of it. However, this "minitower" type unit is typically placed on the floor where accessibility to drives (floppy and CD-ROM), power, and system activity (LEDs) is compromised and awkward. These two form factors (the "desktop" and "minitower" systems) have endured for quite some time with just various changes in the size, shape and color.
Recently, an additional form factor has been developed. The above related applications describe a split system personal computer form factor that significantly reduces the amount of desktop space needed, reduces noise on the desktop and provides easy accessibility to removable DASD drives. For example, the above related application Ser. No. 08/721,650 describes a computer system that includes a media console coupled to a system unit with a multi-conductor cable. The media console contains at least one direct access storage device (e.g., floppy disk drive). The system unit is separate from the media console and includes a microprocessor, a non-volatile storage device and a system power supply. The multi-conductor cable has one end coupled to the media console and another end coupled to the system unit for electrically connecting devices in the media console to devices in the system unit. The system unit has a first interface coupled to the expansion bus and the cable, and the console has a second interface coupled to the cable and the direct access storage device in the console.
The above split system personal computer can contain a "split device", that is, a device which exists in both the media console and the processor unit, yet appear to be in only one place. For example, in the split system, two floppy disk drives can be installed, one in the media console and the other in the processor unit. Each floppy disk drive has its own controller. To the operating system, however, this appears as if two floppy drives are connected to the same controller.
Conventional non-split systems with two floppy disk drives only have one floppy drive controller. The floppy control register in the single floppy controller is used to select between the first floppy drive and the second floppy drive. Whenever software or BIOS accesses the floppy disk, it first selects the correct drive using the floppy control register.
However, in the above split system, each of the floppy disk drives are connected to separate floppy disk controllers. Accordingly, using the floppy control register on one controller would have no effect on the floppy disk connected to the other controller. In addition, since the processor unit and the media console both have a floppy disk controller, they each take the same resources from the system. As a result, both controllers cannot be turned on at the same time. If they were, the system unit interface and the planar floppy disk controller would both respond to floppy disk accesses causing a conflict.
It is therefore desirable to provide a split computer system which can control devices which exist in both the media console and the processor unit without having to remove or disable any of the devices in the media console.